The present invention pertains to compositions and methods for plasmid-mediated supplementation. The present invention pertains to compositions and methods that are useful for retarding the growth rate of abnormal cells, tumor progression reduction, prevention of kidney failure, reduction in metastasis, increased survival and other conditions commonly associated with cancer-bearing animals. Some embodiments of the invention can be accomplished by delivering an effective amount of a nucleic acid expression construct that encodes a GHRH or functional biological equivalent thereof into a tissue of a subject and allowing expression of the encoded gene in the subject. For example, when such a nucleic acid sequence is delivered into the specific cells of the subject tissue specific constitutive expression is achieved. Furthermore, external regulation of the GHRH or functional biological equivalent thereof gene can be accomplished by utilizing inducible promoters that are regulated by molecular switch molecules, which are given to the subject. The preferred method to deliver the constitutive or inducible nucleic acid encoding sequences of GHRH or the functional biological equivalents thereof is directly into the cells of the subject by the process of in vivo electroporation. In addition, a treatment for retarding tumor growth, and retarding cachexia or the wasting effects that are commonly associated with tumors is achieved by the delivery of recombinant GHRH or biological equivalent into the subject. Anemia, wasting, tumor growth, immune dysfunction, kidney failure, cancer, decreased life expectancy, and other conditions can be related to a specific cancer, tumor, disease or the effects of a disease treatment. This invention relates to a plasmid-mediated supplementation for:
1) treating anemia in a subject;
2) increasing total red blood cell mass in a subject;
3) decreasing tumor growth in a tumor bearing individual;
4) preventing or reversing the wasting of a subject;
5) reversing abnormal weight loss in a subject;
6) treating immune dysfunction;
7) preventing the onset of kidney failure
8) preventing the onset and/or development of metastasis
9) reversing the suppression of lymphopoesis in a subject; and/or
10) extending life expectancy and increasing survival for the chronically ill subject.
The present invention pertains to compositions and methods that are useful for retarding the growth rate of abnormal cells, tumor progression reduction, prevention of kidney failure, reduction of metastasis, and increased survival in cancer-bearing animals. Overall, the embodiments of the invention can be accomplished by delivering an effective amount of a nucleic acid expression construct that encodes a GHRH or functional biological equivalent thereof into a tissue of a subject and allowing expression of the encoded gene in the subject. For example, when such a nucleic acid sequence is delivered into the specific cells of the subject tissue specific constitutive expression is achieved. Furthermore, external regulation of the GHRH or functional biological equivalent thereof gene can be accomplished by utilizing inducible promoters that are regulated by molecular switch molecules, which are given to the subject. The preferred method to deliver the constitutive or inducible nucleic acid encoding sequences of GHRH or the functional biological equivalents thereof is directly into the cells of the subject by the process of in vivo electroporation. In addition, a treatment for retarding the growth of abnormal cells and tumor growth is achieved by the delivery of recombinant GHRH or biological equivalent into the subject. Anemia, wasting, tumor growth, immune dysfunction, kidney failure, cancer, decreased life expectancy, and other conditions also can be related to a specific cancer, tumor, disease or the effects of a disease treatment GHRH could be also delivered directly, as protein, by intravenous, subcutaneous or intranasal administration or through a slow release pump.
Anemia: Anemia refers to a condition in which there is a reduction of the number or volume of red blood corpuscles or of the total amount of hemoglobin in the bloodstream, resulting in paleness, generalized weakness, etc. of the subject. The production of red blood cells in mammals is known as erythropoiesis. Erythropoiesis is primarily controlled by erythropoietin (“EPO”), an acidic glycoprotein. The EPO stimulates the production of new erythrocytes to replace those lost to the aging process. Additionally, EPO production is stimulated under conditions of hypoxia, wherein the oxygen supply to the tissues is reduced below normal physiological levels despite adequate perfusion of the tissue by blood. Hypoxia may be caused by hemorrhaging, radiation-induced erythrocyte destruction, various anemia's, high altitude, or long periods of unconsciousness. In response to tissues undergoing hypoxic stress, EPO will increase red blood cell production by stimulating the conversion of primitive precursor cells in the bone marrow into proerythroblasts that subsequently mature, synthesize hemoglobin and are released into the circulation as red blood cells.
EPO is normally present in low concentrations in plasma, where it is sufficient to maintain equilibrium between normal blood cell loss (i.e., through aging) and red blood cell production. Anemia is a decrease in red blood cell mass caused by decreased production or increased destruction of red blood cells. EPO supplementation is currently used for treatment of the anemia's associated with different diseases, as end-stage renal failure (Cremagnani et al., 1993; Diez et al., 1996) and acquired immunodeficiency syndrome (“AIDS”) (Sowade et al., 1998), particularly in subjects who are being treated with zidovudine (“AZT”). EPO is also used for amelioration of the anemia associated with cancer chemotherapy (Vansteenkiste et al., 2002).
Another group of anemic disorders, each of which results from an inherited abnormality in globin production, is termed the hemoglobinopathies. Hemoglobinopathies include a spectrum of disorders that can be classified broadly into two types. The first types are those that result from an inherited structural alteration in one of the globin chains, for example sickle cell anemia. These disorders give rise to the production of abnormal hemoglobin molecules (Papassotiriou et al., 2000). The second major subdivision of hemoglobinopathies, the thalassemias, results from inherited defects in the rate of synthesis of one or more of the globin chains. This causes ineffective erythropoiesis, hemolysis, and varying degrees of anemia due to the inadequate production of red blood cells. Accordingly, EPO can be used in the treatment of anemia's, for example, hemoglobinopathies that are characterized by low or defective red blood cell production and/or increased red blood cell destruction (Makis et al., 2001; Payen et al., 2001).
Additional prior art has indicated that anemic patients with panhypopituitarism, a condition in which hemoglobin (“Hb”) concentration remained as low as 11.0 g/dl in spite of appropriate replacement with thyroid and adrenocortical hormones, were treated with recombinant human growth hormone (“GH”) and EPO levels were increased (Sohmiya and Kato, 2000). Recombinant human GH was constantly infused subcutaneously for 12 months, which caused the plasma erythropoietin (“EPO”) levels to nearly double, with a concomitant increase of Hb concentration. When the administration of human GH was interrupted, both plasma EPO levels and Hb concentrations decreased. There was a close correlation between plasma GH and EPO levels before and during the human GH administration. Plasma GH levels were well correlated with Hb concentrations before and during human GH administration. Plasma IGF-I levels were also correlated with Hb concentrations, but not with plasma EPO levels.
U.S. Pat. Nos. 5,846,528 (“the '528 patent”) and 6,274,158 (“the '158 patent”) teach that conditions of anemia can be treated by deliberately increasing erythropoietin (“EPO”). In addition, the '528 patent teaches the use of recombinant adeno-associated virus (“AAV”) virions for delivery of DNA molecules encoding EPO to muscle cells and tissue in the treatment of anemia. The '528 patent shows a direct in vivo injection of recombinant AAV virions into muscle tissue (e.g., by intramuscular injection), and in vitro transduction of muscle cells that can be subsequently introduced into a subject for treatment. Thus, a sustained high-level expression of a delivered nucleotide sequence encoding erythropoietin results, whereby in vivo secretion from transduced muscle cells allows systemic delivery. The '158 patent teaches the use of the subcutaneous, intravenous or oral administration of recombinant human EPO as a hemostatic agent for the treatment or prevention of bleeding from any organ or body part involved with benign or malignant lesions, surgical traumatic, non-healing/difficult to treat lesions, or radiation injury.
In brief, anemia can be caused by a specific disease, environmental factors, or the effects of a disease treatment. As discussed, circulating levels of EPO can be increased directly (e.g. injections of recombinant EPO) or indirectly (e.g. injections of recombinant GH). Although not wanting to be bound by theory, the related art suggests that anemic conditions can be successfully treated by methods or compounds capable of increasing the circulating levels of EPO. However, a skilled artisan recognizes that biological systems are immeasurably complex, and the ability to accurately predict what methods or compounds will elicit a specific biological response is outside the realm of a skilled artesian. Only through diligent laboratory experiments can insight to compounds or methods to treat anemia be discovered.
Wasting: Wasting of a subject can be defined as decreased body weight of at least 5-10% of the minimum ideal weight of the individual that is characterized by significant loss of both adipose tissue and muscle mass, which makes weight gain especially difficult for patients with a progressive disease (e.g. cancer, AIDS etc.). Wasting or cachexia is a classic clinical phenomenon that evokes historical images of sickbeds and patients with “consumption.” It simply means “poor condition” in Greek. Accelerated loss of skeletal muscle can occur in setting of cancer, AIDS, or tuberculosis, as well as other chronic conditions (Barber et al., 1999; Weinroth et al., 1995). Weight loss is the most obvious manifestation of wasting associated with cancer (Nelson, 2000). Other clinical manifestations include anorexia, muscle wasting, and/or loss of adipose tissue and fatigue, which results in poor performance status (Davis and Dickerson, 2000). Because weight loss, tumor histology, and a poor performance status lead to a poor prognosis, wasting can become the direct cause of death. In contrast to simple starvation, the weight loss cannot be adequately treated with aggressive feeding. The weight loss therefore cannot be attributed entirely to poor intake, but is also a result of increased basal energy expenditure.
Wasting is present in more than one half of ambulatory cancer patients, and represents a serious problem when treating chronically ill patients. Although not wanting to be bound by theory, cytokine release and/or activation and liberation of several tumor derived substances is postulated to be responsible for the wasting syndrome. The related art teaches that many agents have been evaluated for treatment of wasting, with only modest benefit obtained from progestational agents (Barber et al., 1999; Nelson, 2001). In contrast, recombinant growth hormone (“GH”), insulin-like growth factor-I (“IGF-I”) and IGF binding protein 3 (“IGFBP-3”) therapies are effective in producing a benefit in cancer cachexia (Bartlett et al., 1994). Thus, the related art suggests that wasting may be treated by methods or compounds that increase the circulating levels of GH, IGF-I or IGFBP-3. Unfortunately, the complexity of biological systems makes it impossible to accurately predict what methods or compounds will elicit a specific biological response. Thus, only through meticulous laboratory experiments can an insight to useful compounds or methods to treat wasting be elucidated by one skilled in the art.
Cancer and tumor growth: Cancer is one of the leading causes of morbidity and mortality in the US and around the world. The average annual incidence rate for cancer increased in the last 20 years, to reach 475 to 100,000 in 1999. Due to population growth and aging, the number of cancer patient is expected to double from 1.3 million to 2.6 million between 2000 and 2050. In addition, the number and proportion of older persons with cancer are expected to increase dramatically: from 389,000 persons aged 75 years and older with newly diagnosed malignancies in 2000, to 1,102,000 persons in 2050, an increase from 30% to 42% of the cancer population (Edwards et al., 2002). Cancer in elderly has a poor prognosis due to complicating factors as anorexia of aging, alterations in the gastrointestinal system, the effect of elevated leptin levels, especially in men, and a variety of changes in central nervous system neurotransmitters. Body mass declines after the age of about 70 years old. This includes both loss of adipose tissue and muscle mass. The loss of muscle mass in older individuals is termed sarcopenia. Illness results in an increase of cytokines that produce both anorexia and cause protein wasting. Many of the causes of cachexia in older individuals are treatable (Morley, 2001; Yeh and Schuster, 1999). Tumor growth is accelerated by increases in cytokines and other pathological changes in cancer patients, but correction of cachexia, anemia, improvement of immune function and a positive nitrogen balance can decrease tumor growth and its complications (Demetri, 2001; Koo et al., 2001). Thus, a therapy that would address most of these complications could be of important benefit for patients.
Kidney failure: The predicted increase in the number of people with kidney failure and end-stage renal disease places an enormous burden on healthcare providers system (Hostetter and Lising, 2002). In order to reduce this burden, strategies must be implemented to improve the detection of kidney disease, and preventative measures must be targeted at those at greatest risk of disease (Crook et al., 2002). Important risk factors include hypertension, diabetes, obesity and cancer (Al Suwaidi et al., 2002; Nampoory et al., 2002). Serum creatinine, proteinuria, and microalbuminuria as early detection markers of disease are important, but treatments that could delay or prevent kidney failure could be of significant benefit for patients and the medical system (LeBrun et al., 2000; Sakhuja et al., 2000).
Growth Hormone (“GH”) and Immune Function: The central role of growth hormone (“GH”) is controlling somatic growth in humans and other vertebrates, and the physiologically relevant pathways regulating GH secretion from the pituitary is well known. The GH production pathway is composed of a series of interdependent genes whose products are required for normal growth. The GH pathway genes include: (1) ligands, such as GH and insulin-like growth factor-I (“IGF-I”); (2) transcription factors such as prophet of pit 1, or prop 1, and pit 1: (3) agonists and antagonists, such as growth hormone releasing hormone (“GHRH”) and somatostatin (“SS”), respectively; and (4) receptors, such as GHRH receptor (“GHRH-R”) and the GH receptor (“GH-R”). These genes are expressed in different organs and tissues, including the hypothalamus, pituitary, liver, and bone. Effective and regulated expression of the GH pathway is essential for optimal linear growth, as well as homeostasis of carbohydrate, protein, and fat metabolism GH synthesis and secretion from the anterior pituitary is stimulated by GHRH and inhibited by somatostatin, both hypothalamic hormones. GH increases production of IGF-1, primarily in the liver, and other target organs. IGF-I and GH, in turn, feedback on the hypothalamus and pituitary to inhibit GHRH and GH release. GH elicits both direct and indirect actions on peripheral tissues, the indirect effects being mediated mainly by IGF-I.
The immune function is modulated by IGF-I, which has two major effects on B cell development: potentiation and maturation, and as a B-cell proliferation cofactor that works together with interlukin-7 (“IL-7”). These activities were identified through the use of anti-IGF-I antibodies, antisense sequences to IGF-I, and the use of recombinant IGF-I to substitute for the activity. There is evidence that macrophages are a rich source of IGF-I. The treatment of mice with recombinant IGF-I confirmed these observations as it increased the number of pre-B and mature B cells in bone marrow (Jardieu et al., 1994). The mature B cell remained sensitive to IGF-I as immunoglobulin production was also stimulated by IGF-I in vitro and in vivo (Robbins et al., 1994).
The production of recombinant proteins in the last 2 decades provided a useful tool for the treatment of many diverse conditions. For example, GH-deficiencies in short stature children, anabolic agent in burn, sepsis, and AIDS patients. However, resistance to GH action has been reported in malnutrition and infection. Long-term studies on transgenic animals and in patients undergoing GH therapies have shown no correlation in between GH or IGF-I therapy and cancer development. GH replacement therapy is widely used clinically, with beneficial effects, but therapy is associated several disadvantages: GH must be administered subcutaneously or intramuscularly once a day to three times a week for months, or usually years; insulin resistance and impaired glucose tolerance; accelerated bone epiphysis growth and closure in pediatric patients (Blethen and MacGillivray, 1997; Blethen and Rundle, 1996).
In contrast, essentially no side effects have been reported for recombinant GHRH therapies. Extracranially secreted GHRH, as mature peptide or truncated molecules (as seen with pancreatic islet cell tumors and variously located carcinoids) are often biologically active and can even produce acromegaly (Esch et al., 1982; Thorner et al., 1984). Administration of recombinant GHRH to GH-deficient children or adult humans augments IGF-I levels, increases GH secretion proportionally to the GHRH dose, yet still invokes a response to bolus doses of recombinant GHRH (Bercu et al., 1997). Thus, GHRH administration represents a more physiological alternative of increasing subnormal GH and IGF-I levels (Corpas et al., 1993).
GH is released in a distinctive pulsatile pattern that has profound importance for its biological activity (Argente et al., 1996). Secretion of GH is stimulated by the GHRH, and inhibited by somatostatin, and both hypothalamic hormones (Thorner et al., 1995). GH pulses are a result of GHRH secretion that is associated with a diminution or withdrawal of somatostatin secretion. In addition, the pulse generator mechanism is timed by GH-negative feedback. The endogenous rhythm of GH secretion becomes entrained to the imposed rhythm of exogenous GH administration. Effective and regulated expression of the GH and insulin-like growth factor-I (“IGF-I”) pathway is essential for optimal linear growth, homeostasis of carbohydrate, protein, and fat metabolism, and for providing a positive nitrogen balance (Murray and Shalet, 2000). Numerous studies in humans, sheep or pigs showed that continuous infusion with recombinant GHRH protein restores the normal GH pattern without desensitizing GHRH receptors or depleting GH supplies as this system is capable of feed-back regulation, which is abolished in the GH therapies (Dubreuil et al., 1990; Vance, 1990; Vance et al., 1985). Although recombinant GHRH protein therapy entrains and stimulates normal cyclical GH secretion with virtually no side effects, the short half-life of GHRH in vivo requires frequent (one to three times a day) intravenous, subcutaneous or intranasal (requiring 300-fold higher dose) administration. Thus, as a chronic treatment, GHRH administration is not practical.
Wild type GHRH has a relatively short half-life in the circulatory system, both in humans (Frohman et al., 1984) and in farm animals. After 60 minutes of incubation in plasma 95% of the GHRH(1-44)NH2 is degraded, while incubation of the shorter (1-40)OH form of the hormone, under similar conditions, shows only a 77% degradation of the peptide after 60 minutes of incubation (Frohman et al., 1989). Incorporation of cDNA coding for a particular protease-resistant GHRH analog in a therapeutic nucleic acid vector results in a molecule with a longer half-life in serum, increased potency, and provides greater GH release in plasmid-injected animals (Draghia-Akli et al., 1999), herein incorporated by reference). Mutagenesis via amino acid replacement of protease sensitive amino acids prolongs the serum half-life of the GHRH molecule. Furthermore, the enhancement of biological activity of GHRH is achieved by using super-active analogs that may increase its binding affinity to specific receptors (Draghia-Akli et al., 1999).
Extracranially secreted GHRH, as processed protein species GHRH(1-40) hydroxy or GHRH(1-44) amide or even as shorter truncated molecules, are biological active (Thorner et al., 1984). It has been reported that a low level of GHRH (100 pg/ml) in the blood supply stimulates GH secretion (Corpas et al., 1993). Direct plasmid DNA gene transfer is currently the basis of many emerging nucleic acid therapy strategies and thus does not require viral genes or lipid particles (Aihara and Miyazaki, 1998; Muramatsu et al., 2001). Skeletal muscle is target tissue, because muscle fiber has a long life span and can be transduced by circular DNA plasmids that express over months or years in an immunocompetent host (Davis et al., 1993; Tripathy et al., 1996). Previous reports demonstrated that human GHRH cDNA could be delivered to muscle by an injectable myogenic expression vector in mice where it transiently stimulated GH secretion to a modes extent over a period of two weeks (Draghia-Akli et al., 1997).
Administering novel GHRH analog proteins (U.S. Pat. Nos. 5,847,066; 5846,936; 5,792,747; 5,776,901; 5,696,089; 5,486,505; 5,137,872; 5,084,442, 5,036,045; 5,023,322; 4,839,344; 4,410,512, RE33,699) or synthetic or naturally occurring peptide fragments of GHRH (U.S. Pat. Nos. 4,833,166; 4,228,158; 4,228,156; 4,226,857; 4,224,316; 4,223,021; 4,223,020; 4,223,019) for the purpose of increasing release of growth hormone have been reported. A GHRH analog containing the following mutations have been reported (U.S. Pat. No. 5,846,936): Tyr at position 1 to His; Ala at position 2 to Val, Leu, or others; Asn at position 8 to Gln, Ser, or Thr; Gly at position 15 to Ala or Leu; Met at position 27 to Nle or Leu; and Ser at position 28 to Asn. The GHRH analog is the subject of U.S. patent application Ser. No. 09/624,268 (“the '268 patent application”), which teaches application of a GHRH analog containing mutations that improve the ability to elicit the release of growth hormone. In addition, the '268 patent application relates to the treatment of growth deficiencies; the improvement of growth performance; the stimulation of production of growth hormone in an animal at a greater level than that associated with normal growth; and the enhancement of growth utilizing the administration of growth hormone releasing hormone analog and is herein incorporated by reference.
U.S. Pat. No. 5,061,690 is directed toward increasing both birth weight and milk production by supplying to pregnant female mammals an effective amount of human GHRH or one of it analogs for 10-20 days. Application of the analogs lasts only throughout the lactation period. However, multiple administrations are presented, and there is no disclosure regarding administration of the growth hormone releasing hormone (or factor) as a DNA molecule, such as with plasmid mediated therapeutic techniques.
U.S. Pat. Nos. 5,134,120 (“the '120 patent”) and 5,292,721 (“the '721 patent”) teach that by deliberately increasing growth hormone in swine during the last 2 weeks of pregnancy through a 3 week lactation resulted in the newborn piglets having marked enhancement of the ability to maintain plasma concentrations of glucose and free fatty acids when fasted after birth. In addition, the 120 and 721 patents teach that treatment of the sow during lactation results in increased milk fat in the colostrum and an increased milk yield. These effects are important in enhancing survivability of newborn pigs and weight gain prior to weaning. However the 120 and 721 patents provide no teachings regarding administration of the growth hormone releasing hormone as a DNA form.
Gene Delivery and in vivo Expression: Recently, the delivery of specific genes to somatic tissue in a manner that can correct inborn or acquired deficiencies and imbalances was proved to be possible (Herzog et al., 2001; Song et al., 2001; Vilquin et al., 2001). Gene-based drug delivery offers a number of advantages over the administration of recombinant proteins. These advantages include the conservation of native protein structure, improved biological activity, avoidance of systemic toxicities, and avoidance of infectious and toxic impurities. In addition, nucleic acid vector therapy allows for prolonged exposure to the protein in the therapeutic range, because the newly secreted protein is present continuously in the blood circulation. In a few cases, the relatively low expression levels achieved after simple plasmid injection, are sufficient to reach physiologically acceptable levels of bioactivity of secreted peptides (Danko and Wolff, 1994; Tsurumi et al., 1996).
The primary limitation of using recombinant protein is the limited availability of protein after each administration. Nucleic acid vector therapy using injectable DNA plasmid vectors overcomes this, because a single injection into the patient's skeletal muscle permits physiologic expression for extensive periods of time (WO 99/05300 and WO 01/06988). Injection of the vectors promotes the production of enzymes and hormones in animals in a manner that more closely mimics the natural process. Furthermore, among the non-viral techniques for gene transfer in vivo, the direct injection of plasmid DNA into muscle tissue is simple, inexpensive, and safe.
In a plasmid-based expression system, a non-viral gene vector may be composed of a synthetic gene delivery system in addition to the nucleic acid encoding a therapeutic gene product. In this way, the risks associated with the use of most viral vectors can be avoided. The non-viral expression vector products generally have low toxicity due to the use of “species-specific” components for gene delivery, which minimizes the risks of immunogenicity generally associated with viral vectors. Additionally, no integration of plasmid sequences into host chromosomes has been reported in vivo to date, so that this type of nucleic acid vector therapy should neither activate oncogenes nor inactivate tumor suppressor genes. As episomal systems residing outside the chromosomes, plasmids have defined pharmacokinetics and elimination profiles, leading to a finite duration of gene expression in target tissues.
Efforts have been made to enhance the delivery of plasmid DNA to cells by physical means including electroporation, sonoporation, and pressure. Administration by electroporation involves the application of a pulsed electric field to create transient pores in the cellular membrane without causing permanent damage to the cell. It thereby allows for the introduction of exogenous molecules (Smith and Nordstrom, 2000). By adjusting the electrical pulse generated by an electroporetic system, nucleic acid molecules can travel through passageways or pores in the cell that are created during the procedure. U.S. Pat. No. 5,704,908 describes an electroporation apparatus for delivering molecules to cells at a selected location within a cavity in the body of a patient. These pulse voltage injection devices are also described in U.S. Pat. Nos. 5,439,440 and 5,702,304, and PCT WO 96/12520, 96/12006, 95/19805, and 97/07826.
Recently, significant progress has been obtained using electroporation to enhance plasmid delivery in vivo. Electroporation has been used very successfully to transfect tumor cells after injection of plasmid (Lucas et al., 2002; Matsubara et al., 2001) or to deliver the anti-tumor drug bleomycin to cutaneous and subcutaneous tumors in humans (Gehl et al., 1998; Heller et al., 1996). Electroporation also has been extensively used in mice (Lesbordes et al., 2002; Lucas et al., 2001; Vilquin et al., 2001), rats (Terada et al., 2001; Yasui et al., 2001), and dogs (Fewell et al., 2001) to deliver therapeutic genes that encode for a variety of hormones, cytokines or enzymes. Our previous studies using growth hormone releasing hormone (“GHRH”) showed that plasmid therapy with electroporation is scalable and represents a promising approach to induce production and regulated secretion of proteins in large animals and humans (Draghia-Akli et al., 1999; Draghia-Akli et al., 2002).
The ability of electroporation to enhance plasmid uptake into the skeletal muscle has been well documented, as described above. In addition, plasmid formulated with poly-L-glutamate (“PLG”) or polyvinylpyrolidone (PVP) has been observed to increase plasmid transfection and consequently expression of the desired transgene. The anionic polymer sodium PLG could enhance plasmid uptake at low plasmid concentrations, while reducing any possible tissue damage caused by the procedure. The ability of electroporation to enhance plasmid uptake into the skeletal muscle has been well documented, as previously described. PLG is a stable compound and resistant to relatively high temperatures (Dolnik et al., 1993). PLG has been previously used to increase stability in vaccine preparations (Matsuo et al., 1994) without increasing their immunogenicity. It also has been used as an anti-toxin post-antigen inhalation or exposure to ozone (Fryer and Jacoby, 1993). In addition, plasmid formulated with PLG or polyvinylpyrrolidone (PVP) has been observed to increase gene transfection and consequently gene expression to up to 10 fold in the skeletal muscle of mice, rats and dogs (Fewell et al., 2001; Mumper et al., 1998). PLG has been used to increase stability of anti-cancer drugs (Li et al., 2000) and as “glue” to close wounds or to prevent bleeding from tissues during wound and tissue repair (Otani et al., 1996; Otani et al., 1998).
Although not wanting to be bound by theory, PLG will increase the transfection of the plasmid during the electroporation process, not only by stabilizing the plasmid DNA, and facilitating the intracellular transport through the membrane pores, but also through an active mechanism. For example, positively charged surface proteins on the cells could complex the negatively charged PLG linked to plasmid DNA through protein-protein interactions. When an electric field is applied, the surface proteins reverse direction and actively internalize the DNA molecules, process that substantially increases the transfection efficiency. Furthermore, PLG will prevent the muscle damage associated with in vivo plasmid delivery (Draghia-Akli et al., 2002a) and will increase plasmid stability in vitro prior to injection.
The use of directly injectable DNA plasmid vectors has been limited in the past. The inefficient DNA uptake into muscle fibers after simple direct injection has led to relatively low expression levels (Prentice et al., 1994; Wells et al., 1997) In addition, the duration of the transgene expression has been short (Wolff et al., 1990). The most successful previous clinical applications have been confined to vaccines (Danko and Wolff, 1994; Tsurumi et al., 1996).
Although there are references in the art directed to electroporation of eukaryotic cells with linear DNA (McNally et al., 1988; Neumann et al., 1982) (Toneguzzo et al., 1988) (Aratani et al., 1992; Nairn et al., 1993; Xie and Tsong, 1993; Yorifuji and Mikawa, 1990), these examples illustrate transfection into cell suspensions, cell cultures, and the like, and the transfected cells are not present in a somatic tissue.
U.S. Pat. No. 4,956,288 is directed to methods for preparing recombinant host cells containing high copy number of a foreign DNA by electroporating a population of cells in the presence of the foreign DNA, culturing the cells, and killing the cells having a low copy number of the foreign DNA.
U.S. Pat. No. 5,874,534 (“the '534 patent”) and U.S. Pat. No. 5,935,934 (“the '934 patent”) describe mutated steroid receptors, methods for their use and a molecular switch for nucleic acid vector therapy, the entire content of each is hereby incorporated by reference. A molecular switch for regulating expression in nucleic acid vector therapy and methods of employing the molecular switch in humans, animals, transgenic animals and plants (e.g. GeneSwitch®) are described in the '534 patent and the '934 patent. The molecular switch is described as a method for regulating expression of a heterologous nucleic acid cassette for nucleic acid vector therapy and is comprised of a modified steroid receptor that includes a natural steroid receptor DNA binding domain attached to a modified ligand binding domain. The modified binding domain usually binds only non-natural ligands, anti-hormones or non-native ligands. One skilled in the art readily recognizes natural ligands do not readily bind the modified ligand-binding domain and consequently have very little, if any, influence on the regulation or expression of the gene contained in the nucleic acid cassette.
In summary, treatments for conditions such as anemia, wasting and immune dysfunction are uneconomical and restricted in scope. The related art has shown that it is possible to treat these different disease conditions in a limited capacity utilizing recombinant protein technology, but these treatments have some significant drawbacks. It has also been taught that nucleic acid expression constructs that encode recombinant proteins are viable solutions to the problems of frequent injections and high cost of traditional recombinant therapy. The introduction of point mutations into the encoded recombinant proteins was a significant step forward in producing proteins that are more stable in vivo than the wild type counterparts. Unfortunately, each amino acid alteration in a given recombinant protein must be evaluated individually, because the related art does not teach one skilled in the art to accurately predict how changes in structure (e.g. amino-acid sequences) will lead to changed functions (e.g. increased or decreased stability) of a recombinant protein. Therefore, the beneficial effects of nucleic acid expression constructs that encode expressed proteins can only be ascertained through direct experimentation. There is a need in the art to expanded treatments for subjects with a disease by utilizing nucleic acid expression constructs that are delivered into a subject and express stable therapeutic proteins in vivo.